The depth under water, d, in metres, of Daisy the dolphin during a dive can be modelled by the quadratic equation d = 2x2 - 28x + 80 where t is the time in seconds after the dolphin begins her descent towards the water.

How long was Daisy underwater?
seconds.

What was Daisy's lowest depth under water?
18
feet.

How long did it take Daisy to reach her lowest depth?
seconds.

What was Daisy's height when she began her downward dive?
feet.

How deep underwater was Daisy 9 seconds after the dive?